Preparation of a biodegradable packaging film by konjac glucomannan/sodium alginate reinforced with nitrogen-doped carbon quantum dots from crayfish shell for crayfish meat preservation.

The development of biomass material is an important approach to alleviating the excessive using of plastic packaging, by which the product could be more environmentally friendly and lower toxicity. In this study, we developed a biodegradable photodynamic antibacterial food packaging film using nitrogen-doped carbon quantum dots (N-CQDs) synthesized from crayfish shells, combined with konjac glucomannan (KGM) and sodium alginate (SA). Casting method was used to prepare the composite film and results indicated that incorporation of N-CQDs significantly enhanced the mechanical and barrier properties of the film by reducing the number of micropores. The N-CQDs endowed the film with strong antioxidant activity and UV resistance. The DPPH scavenging rate of the composite film reached 77.92 %, while the transmittance of ultraviolet (300 nm) was reduced to 16.97 %. Furthermore, under blue light irradiation, the film exhibited excellent photodynamic antibacterial effects against Shewanella putrefaciens and Staphylococcus aureus, achieving inhibition rates of 99.2 % and 98.99 %, respectively. The film solution demonstrated no cytotoxicity, and the composite film preserved crayfish meat for up to 8 days at 4 °C. Furthermore, the film almost completely degrading in soil within 14 days. These findings suggest that the KGM/SA/N-CQD film is a promising degradable antimicrobial material for food packaging applications.